The role of modifiable risk factors (RF), like physical activity (PA), sleep quality, social engagement, and cardiovascular (CV) risk is receiving greater attention to promote the cognitive health of an aging population and reduce risk of Alzheimer's disease. Each of these risk factors is known to be influenced by environmental sources, such as neighborhood walkability, safety, noise, and access to low-cost transportation, retail, and healthy food sources. However, little is known about the role of neighborhood factors as drivers of cognitive aging and risk for Alzheimer's disease. If neighborhood matters, adaptations in the use of available infrastructures have the potential to impact thousands at a time. Those neighborhood factors that most impact individual RF and cognitive health to reduce Alzheimer's disease risk may further differ by race and sex. Evaluating the role of neighborhood characteristics on cognitive health is difficult to interpret from more widely used cross-sectional data due to residual confounding. Therefore, investigating how residentially stable older adults are affected by their local stable and changing contexts and how older adults who relocate to a new neighborhood may respond to their new context by changing health behaviors requires long-term study during the last 1/3 of life years prior to the onset of Alzheimer's disease. The Cardiovascular Health Study (CHS) represents an ideal cohort for studying interactions between individual health and neighborhood risk factors for various reasons. First, participants were well characterized for key modifiable RF, above, as well as cognition, and mobility. Second, the cohort is nationally representative, bi-racial and spans socioeconomically diverse, urban and rural neighborhoods, allowing us to examine the relation between individual risk and variability in neighborhood factors. Third, our proposal seeks to address the research challenges and opportunities articulated in the NIA Health Disparities Research Framework by examining interactions between environment, biology and behavior. We hypothesize that long-term exposure to neighborhood disadvantage may serve as a common cause of individual risk factors and neurocognitive and functional health, particularly in socio-demographically at-risk groups. Specific aims are to characterize associations between long-term neighborhood exposures and: 1) individual rates of decline and impairment in cognition and physical function; 2) individual risk factors (PA, sleep quality, social engagement and CV burden) for Alzheimer's disease, which may mediate neighborhood differences in cognitive and functional risk, and; 3) whether specific neighborhood exposures account for racial and sex differences in cognitive and functional risk. Addressing these questions in the CHS provides an unmatched opportunity to examine the influence of a range of neighborhood factors on long-term trajectories of cognitive and functional aging prior to the onset of Alzheimer's disease. This work will inform future design of multi-level approaches to target those neighborhood factors impacting multiple RF to optimize healthful activity, reduce health disparities, and help adults remain active and age in place. 1